Reaction propulsion engine and method of operation

ABSTRACT

1. The method of operating an air-breathing propulsion system comprising transferring a portion of energy from the ram air of the system to the fuel supply by indirect heat exchange between the ram air and the fuel at the ram air intake into the system, utilizing at least a portion of the heat transferred to the fuel to further compress at least a portion of the ram air prior to combustion of said portion of the fuel, controlling said further compression of the ram air by bypassing with respect to said further compression a portion of the ram air heated fuel, burning at least a portion of the fuel in the fuel cooled ram air, and expanding the combustion products and uncombusted fuel through at least one reaction expansion nozzle.

llmted States Pate 11 1 [111 3,747,339 olf et al. July 24, 1973 [S41 REACTION PROPULSION ENGINE AND 2,620,625 12/1952 Phanery 60/35.6 METHOD OF ER I 3,016,693 1/1962 Jack 60/355 3,040,519 6/1962 Rae 60/356 1 Inventors: Robert Well, Chesterfield 3,093,348 6/1963 Schelp 60/356 LL County; Christopher J. Cowlin, I Rlchmond, both of Primary Examiner-Verlin R. Pendegrass [73] Assignee: Texaco, Inc., New York, NY. Att0mey stowen and Stowe" PP 152,097 1, The method of operating an air-breathing propulsion system comprising transferring a portion of energy 52 us. Cl 60/206 60/267 60/270 from the the System to fuel Supply by 511 1111131. .3 F0211 11/02 heat exchange between and the fuel [58] Field 61 Search 60/35.6 35.3 35 6 LL the the System utilizing has? 7 7 6 6 a portion of the heat transferred to the fuel to further compress at least a portion of the ram air prior to com- [56] References Cited bustion of said portion of the fuel, controlling said further compression of the ram air by bypassing with UNITED STATTES PATENTS respect to said further compression a portion of the 1 2 2;; a 60/3971 ram air heated fuel, burning at least a portion of the 2483O45 951949 23 fuel in the fuel cooled ram air, and expanding the 2:53l:76l 11/1950 ZUCI'YOQZI... 60/356 combustion Products and combusted fuel through at least one reaction expansion nozzle.

5 Claims, 5 Drawing Figures PATENTEDJULZMQYS SHEEF 1 0F 2 FUEL INVENTORS ROBERT L WOLF CHRISTOPHER J. COWLIN ATTORNEYS PAIENIEmumma I 3.747. 339

W! 2 BF 1;

INVENTOR ROBERT L ,WOLF' CHRISTOPHER J. COWLIN ATTORNEYS REACTION PIRGPULSION lENGllNlE AND METHOD OF OPERATION This invention relates to reaction propulsion engines and method of operating them and particularly to airbreathing reaction propulsion engines capable of efficient operation at hypersonic speeds, especially at speeds in the range between Mach l and Mach 20, as well as being useful for booster operation to such speeds.

The use of rocket propulsion for cruising at speeds of Mach -20 is undesirable because of the inherently low fuel impulse value of chemical rocket systems. The usual ramjet cycles are unattractive at hypersonic speeds because at speeds above about Mach 8 the amount of energy in the inlet is so great that additional heat liberated by fuel combustion in the ram air is mainly absorbed by dissociation of the components of the combustion gases. The energy absorbed by fuel or combustion product dissociation is only partially recovered by recombination during the expansion process.

In the engine and method of the present invention these difficulties are avoided by transferring a portion of the energy of the ram air to the fuel by heat exchange between the ram air and the fuel and utilizing the energy thus transferred by expanding the fuel in an impulse reaction nozzle or in a turbine driving an air compressor or in both ways.

For high cooling efficiency it is desirable that the fuel selected have a high specific heat within the operating temperature range to provide a high absorption of energy per pound of fuel. For efficient conversion of energy to thrust in the expansion process, the fuel should be one which provides a low average molecular weight in the exhaust gases. Within these limitations a considerable range of fuels is available from which selection may be made in the light of other properties of the fuels and their effect on the particular demands to be made on the engine. Among the fuels of interest are hydrogen and hydrogen-bearing compounds such as ammonia, ethyl alcohol, methane and cyclohexane, aswell as low molecular weight metals such as lithium, beryllium and boron and their compounds.

After having cooled the ram air, a portion of the fuel may be burned stoichiometrically with the air without excessive exit temperatures or dissocation energy losses, while the remaining fuel is expanded directly to the atmosphere through a separate thrust nozzle, the proportion thus expanded being determined by the maximum exhaust gas temperature or degree of dissociation desired to be maintained. This portion of the fuel may be partially expanded in the turbine of a turbo-compressor and thereafter finally expanded through the thrust nozzle.

All of the fuel may be expanded in the turbine of a turbo-compressor or in an expander nozzle exhausting directly into a combustor. In both of these arrangements approximately stoichiometric combustion is desirable when the engine is operating as a booster through low Mach number ranges while fuel-rich combustion is desirable at Mach numbers above about 3 where inlet air temperatures are higher in order to keep the combustor temperatures at the desired level.

In general, the ram air is cooled by heat exchange with the fuel sufficiently to avoid excessive exit temperatures and dissociation energy loss, preferably to below about l,O00F. However, cooling of the ram air to such an extent that any substantial portion thereof falls below its condensation temperature at the existing pressure is avoided.

The propulsion systems of the invention offer a number of advantages over previously proposed ramjet systems in providing increased specific thrust, referred both to air and to fuel flow, in providing efficient operation over a wider range of flight speeds up to hypersonic cruising speeds and in reducing the size of the high temperature zones of the engine permitting greater flexibility in installation and structural designs.

The invention will be more fully described with reference to the accompanying drawings in which:

FIGS. 1-4 are diagrammatic representations of various propulsion systems embodying the principles of the invention; and

FIG. 5 is a longitudinal section of a reaction propelled vehicle including a particularly advantageous modification of the propulsion system of FIG. 3.

Referring to the drawings, and in particular to FIG. 1 thereof, there is illustrated one form of the present invention wherein heat absorbed by the fuel from the ram air is utilized prior to combustion of the fuel by expanding the heated fuel through a a fuel-air ejector nozzle exhausting into the combustor and providing an increase in the pressure of the air entering the combustion chamber, thereby improving the engine thrust and impulse. In FIG. 1, It) generally designates a ram air fuel-rich combustor provided with an outlet nozzle 12. Fuel is directed from a fuel storage container 14 through a heat exchanger 16 to at least one expander or fuel-jet air compressor nozzle 1% which discharges directly into the combustion zone 20 of the combustor and has an injector effect on the air entering the combustor as shown and described in US. Pat. No. 1,405,482, Bostedo.

With this arrangement, ram air generally indicated by the arrow 22, after being heated in the air inlet system by conversion of the inlet kinetic energy into static temperature rise, is reduced in temperature by heat transfer to the fuel in the heat exchanger 16. The ram air 22, after having been cooled in passing through the heat exchanger 16, is directed into the primary combustion chamber 20 where the pressure of the ram air is increased by the injector action of the fuel supplied to the expander nozzle 18.

In this form of the invention fuel-rich combustion is desirable particularly when the reaction propulsion vehicle is operating in high Mach number ranges. The

products of combustion are expanded through the nozzle 12. of the combustor 10 to provide thrust for the vehicle.

Where it is desirable to operate the combustor approximately stoichiometrically, even though the overall fuel-air ratio is fuel-rich, a system such as illustrated in FIG. 2 may be employed. In FIG. 2 high temperature ram air 34) is directed through a heat exchanger 32 wherein a portion of the heat is absorbed by the fuel issuing from fuel container 34,. The cooled ram air is then directed into the combustor 3b where it is mixed and stoichiometrically combusted with a portion of the fuel issuing from the heat exchanger 32.

The expanded products of combustion then issue from the exhaust nozzle 38 to provide a portion of the thrust for the reaction vehicle. In FIG. 2 conduit 40 carrying the fuel from the heat exchanger 32 passes through a fuel flow regulating device 42 which directs a portion of fuel into the primary combustor 36 via conduit 44 leading to expander nozzle 45 which exerts an injector effect on the air entering the combustor.

The remainder of the fuel passes from the fuel regulating device 42 via conduit 46 to an expander rocket 48 where the heated fuel is expanded directly to the atmosphere in passing through exit nozzle 50. As previously disclosed, the proportion of the fuel supplied to the primary combustor 36 is determined by the limiting exhaust gas temperature or the degree of dissociation of the fuel desired to be maintained in the combustor 36.

The system of the present invention may also be employed as an air turborocket and all of the heated fuel may be expanded in the turbine of the turbocompressor and the expanded fuel may then be fed to a fuel-rich combustor. Such a system is diagrammatically illustrated in FIG. 3 wherein the heated ram air 60 is first directed through a heat exchanger 62 wherein the fuel from the fuel storage container 64 is heated and directed via conduit 66 to a turbine 68. The turbine 68 is mechanically connected to a compressor 70 for the cooled ram air 60. The compressed ram air issuing from the compressor is directed to a combustor 72 via compressed passage 74.

The expanded fuel issuing from the turbine 68 is also directed to the combustor 72 via conduit 76 where following combustion the combustion products expand through the thrust producing nozzle '78.

Stoichiometrie operation of the combustor of an air turborocket at greater than stoichiometric overall fuelair ratios combines the system illustrated in FIG. 3 with a fuel expander rocket such as illustrated in FIG. 2. Referring to FIG. 4 there is illustrated such a system wherein a portion of the ram air heated fuel is partially expanded in the turbine of a turbo-compressor and thereafter finally expanded through a thrust producing nozzle. In FIG. 4 the hot ram air 80 is cooled to l,000F. or below in passing through a heat exchanger 84 wherein fuel from fuel container 86 is heated. After passing through a fuel divider valve 87, a portion of the heated fuel is expanded in passing through the turbine 88 connected to compressor 90. The partially expanded fuel issuing from the turbine 88 is directed via conduit 92 to an expander rocket 94 having an expansion nozzle 96. That portion of the fuel which is not directed to the turbine 88 is passed to the combustor 98 via conduit 100. After mechanical compression of the rain air 80 in compressor 90, the compressed air is directed to the combustor 98 via air passage 102. The combustion products expand through the nozzle 104 to provide a portion of the thrust for the reaction vehicle.

Referring to FIG. of the drawings, a reaction propelled vehicle is illustrated embodying a particularly advantageous modification of the propulsion system of the present invention wherein the fuel after absorbing the heat from the ram air is passed to a fuel-rich combustor which exhausts to a turbine and the exhaust products issuing from the turbine are combined in a primary combustion chamber with mechanically compressed ram air.

In FIG. 5, 110 designates a reaction engine having an outer shell or casing 112 which is supported from a wing 114 of a vehicle by a strut 116. The forward end 118 of the casing 112 of the reaction engine 1110 is provided with an air inlet compression surface 120 and air inlet passage 122. The air heated in the ram air inlet is directed through a heat exchanger 124 which heat exchanger is connected to the source of fuel (not shown) via the conduit 126.

Within the heat exchanger the fuel absorbs a portion of the heat from the ram air. All of the fuel issuing from the heat exchanger 124 is directed to the annular combustor 132 via at least one fuel conduit 134 connected to the outlet end of the heat exchanger 124. Oxidizer from a source (not shown) is supplied to annular combustor 132 through conduit 127. The fuel-rich products of combustion issue from the combustor 132 directly to the turbine blades 136 of turbine 140. The turbine 140 drives a compressor 142 which mechanically compresses the ram air passing through the heat exchanger 124.

The mechanically compressed air enters the primary combustor 144 via annular compressed air passage 146 and mixes with the fuel-rich exhaust gases from the turbine 140. The combustion products exhaust through exit nozzle 148.

An engine of the type illustrated in FIG. 5 can be operated through the velocity range from static launch to Mach 10-12 at altitudes up to 150,000 200,000 feet, using hydrogen as the fuel and, up to about Mach 3, liquid oxygen as the auxiliary oxidizer. Above about Mach 3, the heat added to the fuel in the heat exchanger 124 gives the fuel enough energy to drive turbine 140 without any auxiliary combustion in combustor 132. The compressor inlet temperature is held below about l,000F. by heat exchange with the fuel.

While only five specific examples of ram air systems employing the principles of the present invention have been specifically illustrated, it will be apparent to those skilled in the art that various modifications therein may be made without departing from the principles of the present invention. For example, the partially expanded fuel issuing from turbine 68 of the form of the invention illustrated in FIG. 3 may be expanded through an expander nozzle exhausting directly into the combustor 72.

We claim:

1. The method of operating an air-breathing propulsion system comprising transferring a portion of energy from the ram air of the system to the fuel supply by indirect heat exchange between the ram air and the fuel at the ram air intake into the system, utilizing at least a portion of the heat transferred to the fuel to further compress at least a portion of the ram air prior to combustion of said portion of the fuel, controlling said further compression of the ram air by bypassing with respect to said further compression a portion of the ram air heated fuel, burning at least a portion of the fuel in the fuel cooled ram air, and expanding the combustion products and uncombusted fuel through at least one reaction expansion nozzle.

2. The method of operating an air-breathing turbocompressor propulsion system comprising transferring a portion of energy from the ram air of the system to the fuel supply by indirect heat exchange between the ram air and the fuel at the ram air intake into the system, utilizing at least a portion of the heat transferred to the fuel to further compress the ram air by direct expansion of at least a portion of the ram air heated fuel prior to combustion of said portion of the fuel through the turbine of a turbo-compressor while passing the cooled ram air through the compressor of the turbocompressor, controlling said further compression of the ram air by bypassing a portion of the ram air heated fuel with respect to the turbine of the turbocompressor, and thereafter burning at least a portion of the fuel in the air compressed by the turbo-compressor and expanding the combustion products and uncombusted fuel through at least one reaction expansion nozzle.

3. A reaction propulsion system including means pro viding a combustion chamber having an outlet nozzle, means providing a ram air intake, means directing air from the ram air intake to the combustion chamber, a fuel storage chamber, heat exchange means in heat exchange contact with the air at the ram air intake of said air directing means upstream of the combustion chamber, means directing fuel from said storage chamber through said heat exchange means, a direct expansion ram air compressing means, means directing uncombusted ram air heated fuel from said heat exchange means through said direct expansion ram air compressing means and means for bypassing a portion of the ram air heated fuel with respect to said direct expansion ram air compressing means.

4. A reaction propulsion system as defined in claim 3 wherein said direct expansion ram air compressing means comprises the turbine of a turbo-compressor positioned in the air directing means upstream of the combustion chamber.

5. A reaction propulsion system including means providing a combustion chamber having an outlet nozzle, means providing a ram air intake, means directing air from the ram air intake to the combustion chamber, a fuel storage chamber, heat exchange means in heat exchange contact with the air at the ram air intake of said air directing means upstream of the combustion chamber, means directing fuel from said storage chamber through said heat exchange means, a direct expansion ram air compression means and means directing uncombusted ram air heated fuel from said heat exchange means through said direct expansion ram air compressing means wherein said direct expansion ram air compressing means comprises a fuel-jet air compressor opening into the combustion chamber. 

1. The method of operating an air-breathing propulsion system comprising transferring a portion of energy from the ram air of the system to the fuel supply by indirect heat exchange between the ram air and the fuel at the ram air intake into the system, utilizing at least a portion of the heat transferred to the fuel to further compress at least a portion of the ram air prior to combustion of said portion of the fuel, controlling said further compression of the ram air by bypassing with respect to said further compression a portion of the ram air heated fuel, burning at least a portion of the fuel in the fuel cooled ram air, and expanding the combustion products and uncombusted fuel through at least one reaction expansion nozzle.
 2. The method of operating an air-breathing turbo-compressor propulsion system comprising transferring a portion of energy from the ram air of the system to the fuel supply by indirect heat exchange between the ram air and the fuel at the ram air intake into the system, utilizing at least a portion of the heat transferred to the fuel to further compress the ram air by direct expansion of at least a portion of the ram air heated fuel prior to combustion of said portion of the fuel through the turbine of a turbo-compressor while passing the cooled ram air through the compressor of the turbo-compressor, controlling said further compression of the ram air by bypassing a portion of the ram air heated fuel with respect to the turbine of the turbo-compressor, and thereafter burning at least a portion of the fuel in the air compressed by the turbo-compressor and expanding the combustion products and uncombusted fuel through at least one reaction expansion nozzle.
 3. A reaction propulsion system including means providing a combustion chamber having an outlet nozzle, means providing a ram air intake, means directing air from the ram air intake to the combustion chamber, a fuel storage chamber, heat exchange means in heat exchange contact with the air at the ram air intake of said air directing means upstream of the combustion chamber, means directing fuel from said storage chamber through said heat exchange means, a direct expansion ram air compreSsing means, means directing uncombusted ram air heated fuel from said heat exchange means through said direct expansion ram air compressing means and means for bypassing a portion of the ram air heated fuel with respect to said direct expansion ram air compressing means.
 4. A reaction propulsion system as defined in claim 3 wherein said direct expansion ram air compressing means comprises the turbine of a turbo-compressor positioned in the air directing means upstream of the combustion chamber.
 5. A reaction propulsion system including means providing a combustion chamber having an outlet nozzle, means providing a ram air intake, means directing air from the ram air intake to the combustion chamber, a fuel storage chamber, heat exchange means in heat exchange contact with the air at the ram air intake of said air directing means upstream of the combustion chamber, means directing fuel from said storage chamber through said heat exchange means, a direct expansion ram air compression means and means directing uncombusted ram air heated fuel from said heat exchange means through said direct expansion ram air compressing means wherein said direct expansion ram air compressing means comprises a fuel-jet air compressor opening into the combustion chamber. 